Vent bag filter



Jam 28, 'i958 R. A. GoDWxN VENT BAG FILTER Filed Jan. 2s, 195s l. .1511.4 l El United States Patent i VENT BAG FILTER Robert A. Godwin, Springfield, Pa., assignor to The Allen-Sherman-Hoff Company, Wynnewood, Pa., a corporation of Pennsylvania Application January 23, 1956, Serial No. 560,485

3 Claims. (Cl. 18S-52) This invention relates to vent filters of the bag type and is particularly concerned with such a filter in which the bag automatically frees itself of the solids it lters out of gases which pass through it.

Vent bag filters have long been used at openings from the tops of silos and other storage structures into which air carrying solids is discharged. The purpose of the lter is to permit the excess air, or other gas, to escape from the chamber of the silo or other storage structure while retaining the solids which were brought into the silo by the air or gas. In many installations the filters are positioned outside of the storage chamber, and in some installations they are sufiiciently exposed to the elements for the solids within the bags to become moist and to adhere to the bag, thereby reducing the eiciency of the filter. In most cases these filters are provided with means by which the solids may be dislodged from the bag, for example, with some sort of bag shaking or vibrating means.

None of the prior vent bag filters with which I am familiar is entirely satisfactory because of their need for means of removing solids from the bag and the nature of the means provided for that purpose.

The present invention aims to provide a vent bag filter which is automatically self-cleaning and is positioned in the silo when not in use as a iilter.

The present invention will be better understood by those skilled in the art from the drawings accompanying and forming a part of this specification in which:

Fig. l is a vertical sectional view showing one embodiment of the present invention associated with a part of a storage silo; and

Fig. 2 is a horizontal cross-sectional view taken on line 2 2 of Fig. l.

In Fig. l the side wall and top of a storage silo are indicated at 1 and 2, respectively. An opening 3 extends upwardly through the top wall 2 of the silo and 'shell 4, preferably composed of metal, is secured yto the wall 2 around opening 3. At its open upper end this shell is provided with a conical metal roof which is spaced above the top of shell 4 far enough to permit free ow of air into and out of the shell. The roof 5 serves to prevent rain, snow, and the like, from entering the upper end of the shell.

Within shell 4 a perforated, relatively rigid guard 6 is disposed in shell 4 and has an outstanding flange at its lower open end by which it may be secured in place around the opening 3. The lower guard 6 is quite like the upper guard 6, but extends down through the opening 3 and has an outstanding flange at its open upper end by which it is secured in place around said opening. These guards 6 and 6' are quite similar in shape and construction and preferably are composed of expanded sheet metal so that they aford large open spaces for gases to pass therethrough and yet are suiiiciently rigid to maintain their shape during use and to limit the extent of movement of the bag.

A bag filter 7 is positioned within one of the guards 2,821,262 Patented Jan. 28, 1958` ice and its open end is secured in place around the opening 3, for example, as by being clamped between the outstanding anges of the upper and lower guard by the means which secure those flanges to the top of the silo. By reference to the drawings it will be noted that the rigid perforated structure comprising upper and lower guards 6 and 6' is at least about twice as long as the bag and that the bag is thereby supported for substantially its full length by this rigid structure whether the bag be in the upper guard or in the lower guard. This bag is made of flexible material which is suiiiciently porous to permit gases to pass therethrough but suliiciently tight to retain fine solids which are brought into the storage chamber by gases traveling at considerable velocity. While various types of textile materials may be used in constructing this bag 7, synthetic fibers have been found to give good satisfaction. For example, Orlon is suitable because it has the necessary strength and resistance to change under varying conditions of the gases, solids and atmosphere, and does not retain moisture.

The above described apparatus operates substantially as follows:

When gases carrying fine solids are discharged with some velocity into the chamber of the silo, the gases pass through the openings in the lower guard and move the bag 7 into the upper guard where it remains as long as the gas pressure in the chamber is suicient to overcome the force of gravity exerted on the bag and any solids which adhere to it. While the gas is thus flowing through the lower guard and through the bag and upper guard, and is escaping from shell 4, the solids which are carried into the bag are collected on what is then the interior of the bag. When the influx of gas into the silo decreases and the force of gravity acting on the bag and its contents of solids is greater than the force of the gases tending to keep the bag in the upper guard, or when a reverse ow of gases occurs due to cooling of the gases within the chamber, the bag will automatically move down into the lower guard turning inside out as it goes and bringing solids collected by it onto the outside of the bag. In this downward movement of the bag many of the solids will be dislodged from the bag. Any moisture which may have been picked up from the elements or by condensation While the bag was in the upper guard will be removed by reason of the temperature prevailing within the interior of the silo. In other words, where the gases which bring the solids into the silo are above room temperature, as is usually the case, the moisture in the bag and solids will be driven ofi and the tendency of the solids to adhere to the bag because of being moist will be overcome and hence there will be no tendency for the solids to adhere to the bag.

Any solids which do adhere to the outside of the bag while it is being turned inside out while being moved into the lower guard, and while it is being dried out while it is in the lower guard will be dislodged therefrom when the next influx of gas turns the bag outside in and moves it into the upper guard. Thus the bag is automatically self-cleaning and requires no special apparatus for performing that function.

Having thus described the present invention so that those skilled in the art may be able to understand and practice the same, I state that what I desire to secure by Letters Patent is defined in what is claimed.

What is claimed is:

l. A lter device comprising an elongated, flexible bag filter open at one end and composed of material sufficiently porous for gases to pass therethrough but substantially impervious to fine solids, and a vertically disposed, perforated, bag supporting structure relatively rigid as compared with .the bag, said structure consisting of an upper member open at its bottom end and a lower member open 3 at its tcgpand eachmember having substantially the-same inside length and transverse dimensions as the bag, the open end of the bag being secured between the open ends -of fsaid members v`and being lsuppented 4fior substantially .its ventitle length #when irr` either vvof said members, saidibag being rmovableavlp-thru itsopen end tand fintosubstantial full length suppontedfengagement*@withfthe innerv surface inner surface :ofisaid :lower :member :by the action ,of

gravity :on the ilter nndfsolidsthereon when-fthe upward members 'haveanges :atftheir f-a`cljaeent op'enfends Jandlin vs'zhic'hfthey open endf-cfy the baglis secured'n place between said iflanges.

The device ef claim 1 in Which'the rigid structure is composedf expanded sheet metal. l

References Cited in the le of this patent UNITED STATES PATENTS 1,220,297 Vanderheof 1;-; Mar. 27, 1917 1,406,299 Sturt et a1. Feb. 14, 1922 2,271,814 CUlge Feb. 3, 1942 2,758,611 4,Silvermanet121.1, ....fAug. 14,1956

FOREIGN PATENTS l 2,881 Great Britain Mar. 25, 1887 yv2r49l7- "Filanl Flm '-27.,"`l1951 62,908 Austria Julyl, 1913 142,855 Sweden` Aug. 27, 1953 

